Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution
Phil R. Bell, Nicolás E. Campione, W. Scott Persons, Philip J. Currie, Peter L. Larson, Darren H. Tanke, Robert T. Bakker
Published 7 June 2017.DOI: 10.1098/rsbl.2017.0092
Abstract
Recent evidence for feathers in theropods has led to speculations that the largest tyrannosaurids, including Tyrannosaurus rex, were extensively feathered. We describe fossil integument from Tyrannosaurus and other tyrannosaurids (Albertosaurus, Daspletosaurus, Gorgosaurus and Tarbosaurus), confirming that these large-bodied forms possessed scaly, reptilian-like skin. Body size evolution in tyrannosauroids reveals two independent occurrences of gigantism; specifically, the large sizes in Yutyrannus and tyrannosaurids were independently derived. These new findings demonstrate that extensive feather coverings observed in some early tyrannosauroids were lost by the Albian, basal to Tyrannosauridae. This loss is unrelated to palaeoclimate but possibly tied to the evolution of gigantism, although other mechanisms exist.
Authors' contributions
P.R.B. conceived and designed the study, acquired data and wrote the manuscript; N.E.C. conceived/performed statistical analyses, acquired/analysed data and wrote the manuscript; W.S.P. analysed the data and wrote the manuscript; P.J.C., P.L.L., D.H.T. and R.T.B. acquired data and critically revised the manuscript. All authors gave final approval for publication and agree to be accountable for all aspects of the work.
Competing interests
We have no competing interests.
Funding
We received no funding for this study.
Acknowledgements
TMP 1994.186.0001 was discovered by Tess Owen. We thank Tess Owen, Tom Owen and S. Kagan for assistance; B. Strilisky (Royal Tyrrell Museum of Palaeontology) for access to specimens; J. Mallon for photographs and information on CMN 11593; and M. Larson for assistance and information on HMNS 2006.1743.01. Silhouette in figure 1 by S. Hartman (phylopic.org). We thank T. Carr, two anonymous reviewers and the handling editor, R. Honeycutt, for insightful comments that improved the final version.
Footnotes
Electronic supplementary material is available online at https://dx.doi.org/10.6084/m9.figshare.c.3787391.
Received February 10, 2017.
Accepted May 15, 2017.
© 2017 The Author(s)
Published by the Royal Society. All rights reserved.
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